PUB TYPE Speeches/Conference Papers (150)-- Reports-

The effects of varying degrees of correlation between abilities and of various correlation configurations between item parameters on ability and item parameter estimation using the three parameter logistic model were examined. Ten two-trait configurations and one unidimensional test configuration for 30 item tests were simulated. Each configuration consisted of a specific item parameter configuration and a specific correlation between traits on two dimension. Six conditions were simulated for each configuration, ranging from an easy to a hard test. The accuracy of item and ability parameter estimation was examined using correlations; KR-20 coefficients and factor analyses were also performed. The factor analyses supported a division of the simulated multidimensional data sets into groups according to the discrimination parameter "loads " on the two dimensions. The tests either both load heavily on bot